Non-dead-centering mechanism



Oct. 23', 1962 w. H. A. BOYD NON-DEAD-CENTERING MECHANISM Filed Oct. 5,1961 3 Sheets-Sheet l FIG. 1C

INVENTOR WILLIAM HUNTER A. BOYD m f W m ft 1 1 w Oct. 23, 1962 w. H. A.BOYD 3,059,498

NON-DEAD-CENTERING MECHANISM Filed Oct. 5, 1961 3 Sheets-Sheet 2 FlG,2

INVENTOR WILLIAM HUNTER A. BOYD BY 45 m ee. 3%.? MW

Oct. 23, 1962 w. H. A. BOYD 3,059,498

NON-DEAD-CENTERING MECHANISM Filed 00 5, 1961 3 Sheets-Sheet a FIG. 4B

INVENTOR WILLIAM HUNTER A. BOYD United States Patent Ofiice 3,059,498Patented Oct. 23, 1962 EJ553458 NON-DEADENTERING MECHANISM WilliamHunter A. Boyd, Kensington, Md., assignor t the United States of Americaas represented by the Secretary of the Army Filed Oct. 5, 1961, Ser. No.143,257 2 Claims. (Cl. 74527) (Granted under Title 35, US. Code (1952),sec. 266) The invention described herein may be manufactured and used byor for the Government for governmental purposes without the payment tome of any royalty thereon.

The present invention relates to a non-dead centering mechanism. Moreespecially, the invention is directed to a mechanical device with whicha rotatable shaft may be set to any selected one of a number ofpredetermined positions. This device simultaneously prevents anydeadcentering of the shaft between successive angular positions. Theshaft in question may be, for example, the control shaft of amultiple-throw rotary electric switch.

When using an electric switch to select the operating parameters ofvarious electrical circuits, it is often necessary to assure unambiguoussetting of the switch to the desired position. In connection withseveral types of electronic fuze for ordnance missiles, the finaladjustments of the fuze circuits before launching are accomplished bymanually presetting the control shaft of a rotary electric switch. Thisfinal setting of the fuze is of utmost importance in tactical use of themissile, since it determines the intensity of the burst as well as thealtitude at which the burst occurs. It is imperative, therefore, thatthese switches be extremely reliable and accurate in their operation.The non-dead centering mechanism of this invention achieves the desiredreliability and accuracy by eliminating the possibility of the controlshafts stopping between switch positions.

An object of the present invention is to improve reliability in thesetting of a rotary or translational switch position selector.

Another object is to prevent inadvertent stopping of a rotary settingdevice between angular positions thereof.

A further object is to provide an improved non-dead centering device ofcompact design having a simple and rugged construction, long life, andease of manufacture.

An additional object is to furnish a non-dead centering mechanism whichhas a detent feel in connection with manual operation.

The specific nature of the invention, as well as other objects, uses andadvantages thereof, will clearly appear from the following descriptionand from the accompanying drawing, in which:

FIG. 1A is a schematic representation of the principal elements formingthe non-dead centering mechanism of this invention.

FIG. 1B is a diagram showing a portion of the stator element togetherwith the rotor spring arm in several different positions.

FIG. 1C is a left end view of the elements in FIG. 1A.

FIG. 2 is an exploded perspective view of a preferred embodiment of theinvention. The non-dead centering mechanism is illustrated together withits shaft coupling members and the electric switch assembly.

FIG. 3 is a sectional View taken on line 3-3 of FIG. 2 showing the dialplate, the stator and the rotor assembled.

FIG. 4A is a further perspective view of the rotor and the stator fromthe side opposite to that shown in FIG. 2.

FIG. 4B is a partial section view taken along line 4-4 in FIG. 4A.

FIG. 5A is an end elevation of the shaft coupling members used in thisinvention.

FIG. 5B is a sectional view on line 5-5 of FIG. 5A.

Referring now to the drawing, wherein like reference numerals designatelike parts, FIG. 1A shows diagrammatically the main components of thenon-dead centering mechanism in conjunction with an electric switch 11.The central control shaft 10 of switch 11 is rotated to somepredetermined angular position to select a desired condition of theswitch contacts. Switch 11 may be any suitable multiple-throw rotaryswitch of known construction. The non-dead centering device comprisesgenerally a stator plate 12 mounted coaxially with control shaft 10 andan indexing arm 15 rigidly connected at one end thereof to the shaft 10.The stator plate 12 serves as a stationary registering member, and forthis purpose contains a plurality of V-shaped notches 13 cut across aportion of one face. A rack section with teeth 14 is formed thereby.Both FIGS. 1A and 1B illustrate this arrangement. The notches 13 must belocated so that the base or bottom of each corresponds to a respectiveone of the predetermined positions of shaft 10.

The indexing arm 15 carries a ball bearing roller 16 which is mounted atthe outer end of arm 15, as seen in FIGS. 1A and 1C. The roller 16initially registers in one of the V-notches 13 and moves successivelyinto the other notches when shaft 10 turns. The arm 15 is a slendercylindrical rod which acts as a cantilever spring as it positions shaft10 with respect to the stator plate 12. It is particularly emphasizedthat indexing spring arm 15 is free to deflect circumferentially withinthe plane of its rotation about shaft 10, as well as normal to thatplane. The cross-section of spring arm 15 is, preferably, eithercircular or square.

In operation, the selector shaft 10 is rotated, either manually or withany suitable automatic driving means, to some particular angularposition corresponding to the desired setting of the various electricalcontacts of switch 11. In conjunction with the afore-mentionedelectronic fuzes, actuation of shaft 10 is preferably manual. FIGS. 1Band 1C are now referred to in describing the operation when controlshaft 10 is rotated. The movement of shaft 10 causes roller 16 to travelfrom any given position a in a first notch 13 to position of in anadjacent notch 13. As shaft 10 turns in the direction of arrow 17,indexing spring arm 15 deflects appreciably, and then causes ballbearing roller 16 to move, first to b and then to the apex of tooth 14at 0. Because of the slope of the walls of notches 13, roller 16 and theouter end of arm 15 both rise vertically, in FIG. 1B. Indexing springarm 15 is deflected both parallel and normal to its plane of rotationabout shaft 10. When arm 15 deflects in the manner described, energy isstored in it. Consequently, spring arm 15 applies a force to the wall ofthe notch '13. This force is represented for point b by vector Fparallel to the plane of rotation, and vector F normal to theaforementioned plane. At the apex of the notch at c, the correspondingcomponents are 'F and 'F 'of larger magnitude. When position c isreached, the portion of the total energy stored in spring arm 15 due toits deflection in the plane of rotation is released,.causing bearingroller 16 to snap over into the bottom of the next notch at d. At pointc the force component F is no longer opposed by the side wall of thefirst notch 13. Therefore, the outer end of arm 15 can travel freelyfrom point 0 in the direction of arrow 17 under the influence of force'F,,, the stored energy being thus released. It is seen that, with thisarrangement, there is no position between a and d where the spring armcould be dead-centered. Even when roller bearing 16 is on the tip of atooth 14, as at 0, there is no possibility of dead-centering, becausethe forces on member 16 are unbalanced. Should shaft 10 not be rotatedfar enough to bring roller 16 to c, then when the torque applied toshaft 10 is removed, part of the energy stored in spring arm 15 willreturn roller 16 back to a, and thus shaft 10 to its initial angularposition.

FIGS. 2 to 4 illustrate the preferred embodiment of the invention, whichincorporates the principles and operation described in connection withFIG. 1A. In FIG. 2, all of the component parts of the non-dead centeringdevice are shown disassembled. The conventional electric switch 11 has acontrol shaft 10 extending a short distance beyond its frame. The statorplate 12 is in the form of a disk with a large central aperture 24 andan upstanding shoulder 25. Notches 13, which have a flat bottom as shownby FIG. 4B, are located in one face of stator 12 opposite shoulder 25,along: a portion of the edge of aperture 24. They do not extend entirelyacross the face of stator 12, as before. See particularly FIG. 4A. Inthe preferredembodiment, intended for use with the fuzes, the indexingspring arm 15 is separately carried by a rotor member 20. Rotor 20, inturn, couples with the switch control shaft 10 through a torque arm 22fitted within a channel member 23. This torque coupling device will bemore completely described subsequently.

A dial plate 27 is adapted to revolve within aperture 24. Dial 27comprises a flat circular disk 28 with an extended rim 2), the diskportion 28 being inserted into aperture 24 with rim 29 abutting shoulder25. A circular boss 30 containing a square hole 31 is centrally locatedin the outer face of dial plate 27. The dial 27 is rigidly secured torotor 20 by four bolts (not shown) passing through holes 32 in dialplate 27 and threaded into tapped holes 39 in rotor 20. With thisarrangement, rotor 20 may be manually positioned with respect to stator12 with a standard Allen wrench inserted in hole 31.

Rotor 20 comprises a drum body 35 together with an integral shaftportion 42. The front face of drum 35 is provided with a radial channel36 of substantial width and depth within which indexing arm 15 ismounted. Referring to FIG. 3, a hole 37 in the end wall of channel 36receives one end of spring arm 15. Hole 37 is oriented at a small anglepreferably of about from an axis parallel to the plane of the face ofstator 12. This allows roller 16 on the other end of arm 15 to registerwithin notches 13. Arm 15 may be securely engaged with rotor 20 by twoset screws (not shown) placed in holes 38 in drum 35. Shaft 42terminates in an end section 43 of reduced diameter.

A torque arm or bar 22 is directly connected to rotor 20 in order torotate with the latter. For this purpose, the end 43 of shaft 42 isinserted in an aperture 45 at one end of arm 22. A coupling stud 47 setwithin a pair of aligned holes 44 and 46 engages torque arm 22 withshaft 42. A generally .U-shaped channel member 23 is positioned so thattorque arm 22 meshes with the inner surfaces of side walls 52 of channel23. Channel 23, in turn, is mounted upon the control shaft which isplaced within an aperture 48 in the base of channel 23. A set screw 50located in a tapped hole 49 at the bottom of channel 23 serves to firmlyclamp the latter to shaft 10.

Each side wall 52 includes a section 53 of greater thickness at theouter end of channel member 23, so that the channel is reduced in widthand thus has a larger clearance for torque arm 22 at the root than atits tip. The

torque coupling device described permits considerable misalignment ofthe axis of rotor 20 with respect to shaft 10, while angular motion istransmitted via tip section 53 with a minimum of angular slack.Therefore, close angular tolerance between the positions of rotor 20 andcontrol shaft 10 is achieved.

The operation of the embodiment illustrated in FIGS. 2-5 is the same asthat set forth above regarding the diagram of FIG. 1A. In brief, stator12 and the frame of switch assembly 11 are affixed to suitablestationary parts of the missile so that dial plate 27 faces outward. Acover plate (not shown) forming a portion of the surface of the missileis removed to gain access to the switch setting device. As dial plate 27and rotor 20 together are turned to the required setting, shaft 10follows the rotation of rotor 20 by reason of its coupling to shaft 42through arm 22 and channel 23. Indexing spring arm 15 and roller 16co-operate with notches 13 in stator 12 in the manner previouslydescribed to establish discrete predetermined rest positions of controlshaft 10. Dial plate 27 may be provided with a suitable indicating scale54 to show the switch position selected.

While the switch positioning device described and illustrated in thedrawing involves rotary motion of the component parts, it should beunderstood that the invention is not limited to configurations involvingrotation, but encompasses longitudinal or translational movement aswell. Further, where desired the indexing spring arm 15 may be mountedupon the stationary member 12 with the series of notches 13 suitablylocated on the rotor 20. Obviously, a larger number of notches 13 may beprovided in stator 12 to establish angular positions of shaft 10 through360 of its rotation. If higher restoring torques produced by spring arm15 are required, with a single spring arm the maximum or limiting stressof available spring materials might be exceeded. In such situations, thespring arm may be formed by a plurality of separate spring membersacting together. It can be shown that the stresses encountered in themultiple spring arrangement will be considerably lower than in a singlespring arm. However, tests performed on single spring arm devices inaccordance with the invention have proved entirely satisfactory. Whilethe invention has been shown controlling an electric switch, thenon-dead centering device is not limited to such applications, but maybe used for any control shaft, for example in the setting ofpotentiometers, valves, or the like.

The non-dead centering mechanism disclosed herein is simple inconstruction and reliable in its operation. Inadvertent mis-setting ofthe electric switch is entirely prevented. The ball bearing roller 16serves to minimize the friction between the relatively moving parts.Since spring arm 15 is strong enough to overcome any friction in thesystem, the necessity for a separate locking means to hold the shaftonce it is set is obviated. Moreover,

the spring action of indexing arm 15 aids in overcoming harmful inertialeffects of the vibrations associated with the missile environment.

It will be apparent that the embodiment shown is only exemplary and thatvarious modifications can be made in construction and arrangement withinthe scope of the invention as defined in the appended claims.

Even though the spring indexing arm 15 is shown with a roller 16 on itsregistering end, it is obvious that, in cases where friction isnegligible, roller 16 can be eliminated and arm 15 be used alone.

I claim as my invention:

1. -A non-dead centering device for unambiguous setting of the controlshaft of an electric switch comprising a stationary disk having acentral aperture, a plurality of notches witln'n said disk, a rotorpositioned within said aperture, a spring indexing arm having one endconnected to said rotor and the other end contacting said notches, saidspring arm deflecting both parallel and normal to the plane of rotationof said spring arm when said rotor is rotated, and means for couplingsaid rotor to said control shaft.

2. A mechanism for positioning the control shaft of a rotary electricswitch at one of a plurality of predetermined positions without stoppingbetween adjacent positions, comprising, in combination: a stationarydisk having a central aperture, a plurality of notches corresponding tosaid switch positions located within said disk, a rotor positionedwithin said aperture, means for applying an input torque to said rotor,a cantilever spring indexing arm carried by said rotor with the free endof said arm registering with said notches, said spring arm deflectingboth parallel and normal to the plane of rotation of said spring armwhen said rotor is rotated, a torque arm rigidly coupled to said rotor,a U-shaped channel having an end section of reduced Width, said torquearm fitting within said channel, and means for rigidly coupling saidcontrol 5 shaft to said channel so that unambiguous setting of saidelectric switch is assured.

References Cited in the file of this patent UNITED STATES PATENTSReynolds May 26, 1959

